Problem: Reduce to simplest form. $-\dfrac{5}{12}-\left(-\dfrac{9}{3}\right)=$
$=-{\dfrac{5}{12}} +{\dfrac{9\cdot4}{3\cdot4}}$ $=-{\dfrac{5}{12}}+{\dfrac{36}{12}}$ $=\dfrac{31}{12}$ or $2\dfrac7{12}$